Modeling the Boat from ‘Apocalypse Now’, Part 2

By Terry Dunn

Terry continues his modification of an RC boat to turn it into the Erebus from Apocalyse Now!

In the first article of this series, I covered the cosmetic changes that I incorporated to make my Alpha Patrol Boat from ProBoat Models look like the Erebus from 'Apocalypse Now'. This time around, I'll talk about mechanical upgrades that I made to the model. These changes were intended to add a little more realism, make the model more dependable, and also make it easier to drive. As before, some of the techniques I tried were new to me and the efficacy of my efforts varied.

Ready, Aim…

The model comes with most of what you need to make the forward gun turret articulate. There is a servo mount inside the hull below the turret. The turret itself has parts to attach it to a standard servo arm. The only thing missing is the actual servo.

I used a Spektrum S605 waterproof servo ($14). It bolted right into the existing mount and the included servo arm mated perfectly with the turret. The boat's manual indicates that you cannot add a servo to the turret if you are using the included 2-channel radio system. That's not entirely true. You can use the stock radio if you connect the turret servo in parallel with the steering servo using a common servo Y-cable. You just will not have independent control of the turret. It will move in response to your steering commends.

I didn't think that I would be coordinated enough to command the turret and drive at the same time. So I was planning to keep the stock radio and connect the turret to my steering channel. As I dug deeper into the project, however, it became clear that my other upgrades would demand a more capable radio. I swapped out the stock radio for a 4-channel Spektrum DX4C pistol-grip controller and SRS4210 receiver. I still slaved the turret to the steering. The DX4C's channel mixing menus allowed me to skip the Y-cable and accomplish the same goal. Less wire is always better.

Closing the Flood Gates

This model takes on more water than any of my other RC boats. It is not unusual to have ¼ to ½ cup of water inside the hull at the end of a 10–minute driving session. I had a hunch that a lot of this water was coming in through the front turret. The bottom of the turret is completely open. So any water that splashes into the top of the turret will flow immediately inside the hull.

I prevented water from entering through the forward gun turret by adding plastic sheet over the bottom opening.

I addressed this concern at the same time that I installed the articulation servo. I sealed off the turret by adding sheet plastic over the bottom opening. This required me to cut away and sand down a couple of protrusions on the turret, but it was easy work. The plastic cover was made from the blister-pack that my 1/18-scale crew members came packaged in. I cut the plastic to size, glued it in place with cyanoacrylate glue (CA, aka "super glue") and sealed the edges with GOOP. The last step was to drill a hole in the plastic for the servo arm screw to protrude through.

The turret sat a little higher once the articulation servo was installed. This left a gap between the turret and the flanged opening in the boat deck. I thought that this new opening would present additional risk of taking on water. I created a skirt for the turret that covers that gap completely. The material I used for the skirt was the faux canvas material that originally served as the wheelhouse roof. This worked out great since the material was flexible and already painted to a matching color.

I cut the material into strips measuring 7/16" wide and 1" long. I then used CA to attach the strips around the perimeter of the turret. To improve the flexibility of the skirt, I added a vertical relief cut to each strip at about the halfway point. The completed skirt effectively seals off the gap but does not affect articulation of the turret.

I created a skirt around the base of the forward turret to cover a gap and keep water out of the hull.

Now that I've explained how I sealed the openings in and around the front turret, I have to admit that it hasn't made much difference. I rarely find much water trapped in the now-sealed turret, but the hull still takes on a considerable volume of water during operation. I need to investigate more thoroughly to track down the primary source of the unwanted water. Even so, I feel better knowing that the turret is closed off and should not cause me any issues.

Sound and Fury

I never planned to add a sound system to this model. I felt like there wasn't sufficient room for the necessary equipment. Yet every time I talked about this project with my buddy, Lee Ray, he insisted that it really needed sound. I kept telling him, "No way", but apparently, the seed had been planted in my brain.

As I was digging through my workshop to find the parts I would need for adding the turret servo, I stumbled upon my Mr. RC Sound V4.1 sound system. I took that discovery as a sign from the universe and began looking to see if I could make it work in the Erebus.

This transducer is part of the Mr. RC Sound System that produces engine and machine gun sounds. It was installed inside the hull below the wheelhouse.

The V4.1 has two main components: a control board and a transducer. The control board connects to the radio receiver in parallel with the throttle channel. As the driver moves the throttle up or down, this board alters the RPM of the simulated engine sound.

The sounds are generated by the transducer. The transducer is basically a speaker without the cone. When you attach the transducer to a flat area of your model, the model itself becomes a speaker.

I attached my transducer inside the hull below the floor of the wheelhouse. It was the only unobstructed flat area to be found. I soon discovered that the mounted transducer obscured the forward part of the battery mounting area. This prevented me from using 6-cell NiMH batteries. I also had to forego using my preferred 2-cell A123 batteries because the nominal voltage of my A123 packs is slightly below the minimum voltage demanded by the sound system. I now use 2S-2250mAh Thunder Power LiPo batteries. They are small enough to fit in the downsized battery area and provide adequate voltage for the sound system.

The extra volume needed for the sound system encouraged me to power the Erebus with this Thunder Power 2S-2250mAh LiPo battery rather than NiMH or A123 packs.

I wanted to protect the sound control board from water, so I housed it inside of a small plastic box. I mounted this box just behind the turret servo inside the hull. The receiver sits atop the box. There are definitely more wires than with the stock configuration, but everything fits without trouble.

I spliced the sound system power leads into the battery wires for the ESC. I also added a mechanical switch. This allows me to drive the boat with or without sounds. I typically do not use sounds on back-to-back runs to prevent overheating the control board in its sealed box.

Adding engine sounds with the V4.1 does not require an additional radio channel. You will need a free channel, however, if you want to incorporate the system's machine gun sound. This feature was the tipping point that encouraged me to trade the stock radio for the DX4C. I set up my system so that the machine gun sound is controlled with a thumb switch on the grip of the transmitter. I can activate it without any impact to my driving.

I placed the control board for the sound system inside of a plastic box to protect it from water.

I have no idea what a real PBR sounds like. They use twin diesel engines that I imagine produce an aggressive, gurgling growl in the water. I scrolled through the sound system's list of airplane engines until I found one that was close to my imaginary boat engine. It may be completely inaccurate, but I do like the way it sounds.

I have to admit that Lee was right. The sound system is a nice accent for this project. It is definitely an attention-getter. The system is most effective when driving the Erebus at slow speeds. Above half-throttle, the sound of the model's actual electric water jets overcomes the emulated engine and gun sounds.

To Everything (Turn, Turn, Turn)

In my original review of the Alpha Patrol Boat, I mentioned that the model is prone to spinning out at high speed. This tendency can be tempered with reduced steering travel and a light touch on the control wheel. The engineer in me wondered if there might be a way to tame the boat and make it less dependent on driving technique. I decided to experiment with turn fins.

A turn fin is basically just a blade that protrudes into the water to help stabilize the boat. It is definitely not a scale feature on the Erebus. Scale purists might even say that adding a turn fin to a PBR model is an unforgiveable sin. Good thing I'm not a purist!

These turn fins were made from aluminum sheet to help prevent unintentional spin-outs when driving at high speed. Only one fin is necessary.

Many of my other RC boats have turn fins made from thin aluminum. I kept to that theme by cutting turn fins from 32/1000"-thick K&S aluminum sheet. The aluminum is really easy to work with. I was able to cut the rough shape with a fine-tooth blade in my band saw. Bending and final shaping was accomplished with my bench vise and a sanding drum in my Dremel tool.

I took a wild guess at the size turn fin I would need for this boat. I actually made two fins that could be mounted at the same time. I didn't want to add any new holes or screws to the model. So I designed the fins such that they attached to the boat using existing hardware on the water-jet housings.

On my first outing with the turn fins installed, it was immediately apparent that using both fins provided too much stability. The boat would hardly turn at all at high-speed! I brought it in and removed one of the turn fins. With just one fin, things were much better. I was able to turn effectively, but I still felt that the boat was now too stable.

My goal was to have a boat that was predictable and maneuverable during normal driving but could be coaxed into a spin with aggressive control inputs. I subsequently experimented by shortening the single fin until I found a size that provided the performance I was after. I settled on a turn fin that is 5/8"-wide and protrudes below the bottom of the hull by 5/8". I think that the addition of this fin has made the model much more enjoyable to drive.

The completed Erebus is a product of numerous small changes and enhancements.

It's a Wrap

As I look back on the numerous steps of this project, it becomes evident that my Erebus is a significantly different model than the box-stock Alpha Patrol Boat that I originally reviewed. I didn't make any drastic singular changes. Rather, the boat evolved with a series of minor tweaks. It was a fun process as I learned some new modeling techniques, integrated different components, and discovered a few things about boat design.

Terry is a freelance writer living in Buffalo, NY. Visit his website at TerryDunn.org and follow him on Twitter and Facebook. You can also hear Terry talk about RC hobbies as one of the hosts of the RC Roundtable podcast.